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Circular  no.  79. 

United  States  Department  of  Agriculture, 

BUREAU  OF  ENTOMOLOGY. 

L.  O.  HOWARD.  Entomologist  and  Chief  of  Bureau. 


THE    I5K001)    DISEASES    OF    BEES. 

By  E.  F.  Phillips,  Ph.  D., 
Apicultural  Kxpert. 

In  view  of  the  widespread  distribution  of  infectious  brood  diseases 
among  bees  in  the  United  States,  it  is  desirable  that  all  bee  keepers 
learn  to  distinguish  the  diseases  when  they  appear.  It  frequently  hap- 
pens that  an  apiary  becomes  badly  infected  before  the  owner  realizes 
that  any  disease  is  present,  or  it  may  be  that  any  dead  brood  which 
may  be  noticed  in  the  hives  is  attributed  to  chilling.  In  this  \N'ciy  dis- 
ease gets  a  start  which  makes  eradication  difficult. 

There  are  two  recognized  forms  of  disease  of  the  brood,  designated  as 
European  and  American  foul  brood,  which  are  particularly  virulent.  In 
some  ways  these  resemble  each  other,  but  there  are  certain  distinguishing 
characters  which  make  it  possible  to  differentiate  the  two.  Reports  are 
sometimes  received  that  a  colony  is  infected  with  both  diseases  at  the 
same  time,  but  this  is  contrary  to  the  experience  of  those  persons  most  con- 
versant with  these  conditions.  While  it  may  be  possible  for  a  colony 
to  have  the  infection  of  both  diseases  at  the  same  time,  it  is  not  by  any 
means  the  rule,  and  such  cases  are  probably  not  authentically  reported. 
Since  both  diseases  are  caused  by  specific  bacilli,  there  is  absolutely 
no  ground  for  the  idea  held  hy  some  bee  keepers  that  chilled  or  starved 
brood  will  turn  to  one  or  the  other  of  these  diseases.  Experience  of 
the  best  practical  observers  is  also  in  keeping  with  this.  For  a  discus- 
sion of  the  causes  of  these  diseases  the  reader  is  referred  to  Technical 
Series,  No.  14,  of  the  Bureau  of  Entomology,  "The  Bacteria  of  the 
Apiary,  with  Special  Reference  to  Bee  Diseases,"  by  Dr.  G.  F.  White. 

AMERICAN    FOUL   BROOD. 

American  foul  brood  (often  called  simply  "  foul  brood  ")  is  distributed 
thru  all  parts  of  the  United  States,  and  from  the  symptoms  published  in 
European  journals  and  texts  one  is  led  to  believe  that  it  is  also  the 
prevalent  brood  disease  in  Europe.  Altho  it  is  found  in  almost  all  sec- 
tions of  the  United  States,  there  are  many  localities  entirely  free  from 
disease  of  any  kind. 

The  adult  bees  of  an  infected  colony  are  usually  rather  inactive  and 
do  little  toward  cleaning  out  infected  material.  When  the  larvae  are 
first  affected  they  turn  to  a  light  chocolate  color,  and  in  the  advanced 
stages  of  decay  they  become  darker,  resembling  roasted  coffee  in  color. 


Usually  the  larvae  are  attacked  at  about  the  time  of  capping,  and  most 
of  the  cells  containing  infected  larvae  are  capped.  As  decay  proceeds 
these  cappings  become  sunken  and  perforated,  and,  as  the  healthy 
brood  emerges,  the  comb  shows  the  scattered  cells  containing  larvae 
which  have  died  of  disease,  still  capped.  The  most  noticeable  charac- 
teristic of  this  infection  is  the  fact  that  when  a  small  stick  is  inserted 
in  a  larva  which  has  died  of  the  disease,  and  slowly  removed,  the 
broken-down  tissues  adhere  to  it  and  will  often  stretch  out  for  several 
inches  before  breaking.  When  the  larva  dries  it  forms  a  tightly  adher- 
ing scale  of  very  dark  brown  color,  which  can  best  be  observed  when 
the  comb  is  held  so  that  a  bright  light  strikes  the  lower  side  wall. 
Decaj'ing  larvae  which  have  died  of  this  disease  have  a  very  character- 
istic odor  which  resembles  a  poor  quality  of  glue.  This  disease  seldom 
attacks  drone  or  queen  larvae.  It  appears  to  be  much  more  virulent  in 
the  western  part  of  the  United  States  than  in  the  East. 

EUROPEAN    FOUL   BROOD. 

European  foul  brood  (often  called  "black  brood")  is  not  nearly'  as 
widespread  in  the  United  States  as  is  American  foul  brood,  but  in  certain 
parts  of  the  country  it  has  caused  enormous  losses.  It  is  steadily  on 
the  increase  and  is  constantly  being  reported  from  new  localities.  It  is 
therefore  desirable  that  bee  keepers  be  on  the  watch  for  it. 

Adult  bees  in  infected  colonies  are  not  very  active,  but  do  suc- 
ceed in  cleaning  out  some  of  the  dried  scales.  This  disease  attacks 
larvae  earlier  than  does  American  foul  brood,  and  a  comparatively 
small  percentage  of  the  diseased  brood  is  ever  capped.  The  diseased 
larvae  which  are  capped  over  have  sunken  and  perforated  cappings. 
The  larvae  when  first  attacked  show  a  small  yellow  spot  on  the  bodj^ 
near  the  head  and  move  uneasily  in  the  cell.  When  death  occurs  they 
turn  yellow,  then  brown,  and  finally  almost  black.  Decaying  larvae 
which  have  died  of  this  disease  do  not  usually  stretch  out  in  a  long 
thread  when  a  small  stick  is  inserted  and  slowl}^  removed.  Occasion- 
ally there  is  a  very  slight  "ropiness,"  but  this  is  never  ver3'  marked. 
The  thoroly  dried  larvae  form  irregular  scales  which  are  not  strongly 
adherent  to  the  lower  side  wall  of  the  cell.  There  is  very  little  odor 
from  decaying  larvae  which  have  died  from  this  disease,  and  when  an 
odor  is  noticeable  it  is  not  the  "  glue-pot"  odor  of  the  American  foul 
brood,  but  more  nearly  resembles  that  of  soured  dead  brood.  This  disease 
attacks  drone  and  queen  larvae  very  soon  after  the  colony  is  infected. 
It  is  as  a  rule  much  more  infectious  than  American  foul  brood  and 
spreads  more  rapidly.  On  the  other  hand,  it  sometimes  happens  that 
the  disease  will  disappear  of  its  own  accord,  a  thing  which  the  author 
never  knew  to  occur  in  a  genuine  case  of  American  foul  brood.  Euro- 
pean foul  brood  is  most  destructive  during  the  spring  and  early  summer, 
often  almost  disappearing  in  late  summer  and  autumn. 


TREATMENT    OF   INFECTIOUS    DISEASES. 

The  treatment  for  both  American  foul  brood  a"^id  European  foul  brood 
is  practically  the  same.  It  is  impossible  to  give  minute  directions  to 
cover  every  case,  but  care  and  common  sense  will  enable  any  bee  keeper 
successfully  to  fight  diseases  of  brood. 

Drugs. — Drugs,  either  to  be  given  directly  in  food  or  to  be  used  for 
fumigating  combs,  can  not  be  recommended  for  either  of  these  diseases. 

Shaking  treatment. — To  cure  a  colony  of  either  form  of  foul  brood  it 
is  necessary  first  to  remove  from  the  hive  all  of  the  infected  material. 
This  is  done  by  shaking  the  bees  into  a  clean  hive  on  clean  frames  with 
small  strips  of  comb  foundation,  care  being  taken  that  infected  honey 
does  not  drop  from  the  infected  combs.  The  healthy  brood  in  the 
infected  combs  may  be  saved,  provided  there  is  enough  to  make  it  profit- 
able, by  piling  up  combs  from  several  infected  hives  on  one  of  the 
weakest  of  the  diseased  colonies.  After  a  week  or  ten  days  all  the  brood 
which  is  w^orth  saving  will  have  hatched  out,  at  which  time  all  these 
combs  should  be  removed  and  the  colony  treated.  In  the  case  of  box 
hives  or  skeps  the  bees  maj^  be  drummed  out  into  another  box  or  pref- 
erably into  a  hive  with  movable  frames.  Box  hives  are  hard  to  inspect 
for  disease  and  are  a  menace  to  all  other  bees  in  the  neighborhood  in 
a  region  wdiere  disease  is  present.  » 

The  shaking  of  the  bees  from  combs  should  be  done  at  a  time 
when  the  other  bees  in  the  apiary  will  not  rob  and  thus  spread  disease, 
or  under  cover.  This  can  be  done  safely  in  the  evening  after  bees  have 
ceased  to  fly,  preferably  during  a  good  honey  flow.  Great  care  should  be 
exercised  to  keep  all  infected  material  aw^ay  from  other  bees  until  it 
can  be  completely  destroyed  or  the  combs  rendered  into  wax.  Wax  from 
diseased  colonies  should  be  rendered  by  some  means  in  which  high  heat- 
ing is  used,  and  not  with  a  solar  wax  extractor.  The  honey  from  a  dis- 
eased colony  should  be  diluted  to  prevent  burning  and  then  thoroly 
sterilized  by  hard  boiling  for  at  least  half  an  hour,  if  it  is  to  be  fed  back 
to  the  bees.  If  the  hive  is  again  used,  it  should  be  very  thoroly  cleaned, 
and  special  care  should  be  taken  that  no  infected  honey  or  comb  be 
left  in  the  hive. 

It  is  frequently  necessary  to  repeat  the  treatment  by  shaking  the  bees 
onto  fresh  foundation  in  new  frames  after  four  or  five  days.  The  bee 
keeper  or  inspector  must  determine  whether  this  is  necessary,  but  when 
there  is  any  doubt  it  is  safer  to  repeat  the  operation  rather  than  run  the 
risk  of  reinfection.  If  repeated,  the  first  new  combs  should  be  destroyed. 
To  prevent  the  bees  from  deserting  the  strips  of  foundation  the  queen 
may  be  caged  in  the  hive  or  a  queen-excluding  zinc  put  at  the 
entrance. 

Treatment  ivitJi  hee  escape. — The  shaking  treatment  may  be  modified 
so  that  instead  of  shaking  the  bees  from  the  combs  the  hive  is  moved 


from  its  stand,  and  in  its  place  a  clean  hive  with  frames  and  founda- 
tion is  set.  The  queen  is  at  once  transferred  to  the  new  hive,  and  the 
field  bees  fly  there  when  they  next  return  from  the  field.  The  infected 
hive  is  then  placed  on  top  of  or  close  beside  the  clean  hive  and  a  bee 
escape  placed  over  the  entrance  of  the  hive  containing  disease,  so  that 
the  younger  bees  and  those  which  later  emerge  from  the  cells  may  leave 
the  hive  but  can  not  return.  They  therefore  join  the  colony  in  the  new 
hive. 

Fall  treatment. — If  it  is  desirable  to  treat  a  colony  so  late  in  the  fall 
that  it  would  be  impossible  for  the  bees  to  prepare  for  winter,  the  treat- 
ment may  be  modified  by  shaking  the  bees  onto  combs  with  plenty  of 
honey  for  winter.  This  will  be  satisfactory  only  after  brood  rearing 
has  entirely  ceased.     In  such  cases  disease  rarely  reappears. 

In  the  Western  States,  where  American  foul  brood  is  particularly 
virulent,  it  is  desirable  thoroly  to  disinfect  the  hive  by  burning  the 
inside  or  by  chemical  means  before  using  it  again.  This  is  not  always 
practised  in  the  Eastern  States,  where  the  disease  is  much  milder. 
Some  persons  recommend  boiling  the  hives  or  disinfecting  them  wdth 
some  reliable  disinfectant  such  as  carbolic  acid  or  corrosive  sublimate. 
It  is  usually  not  profitable  to  save  frames  because  of  their  comparatively 
small  value,  but  if  desired  they  may  be  disinfected.  Great  care  should 
be  exercised  in  cleaning  any  apparatus.  It  does  not  pay  to  treat  very 
weak  colonies.  They  should  either  be  destroyed  at  once  or  several 
weak  ones  be  united  to  make  one  which  is  strong  enough  to  build  up. 

Recently  some  new  "  cures  "  have  been  advocated  in  the  bee  journals, 
particularly  for  European  foul  brood,  with  a  view  to  saving  combs  from 
infected  colonies.  The  cautious  bee  keeper  will  hardly  experiment  with 
such  methods,  especially  when  the  disease  is  just  starting  in  his  local- 
ity or  apiary,  but  will  eradicate  the  disease  at  once  by  means  already 
well  tried. 

In  all  cases  great  care  should  be  exercised  that  the  bee  keeper  maj^ 
not  himself  spread  the  infection  by  handling  healthy  colonies  before 
thoroly  disinfecting  his  hands,  hive  tools,  and  even  smoker.  Since  it 
takes  but  a  very  small  amount  of  infected  material  to  start  disease  in  a 
previously  healthy  colony,  it  is  evident  that  too  much  care  can  not  be 
taken.  In  no  case  should  honey  from  unknown  sources  be  used  for 
feeding  bees.  Care  should  also  be  exercised  in  buying  queens,  since 
disease  is  often  transmitted  in  the  candy  used  in  shipping  cages. 
Combs  should  not  be  moved  from  hive  to  hive  in  infected  apiaries. 


There  is  a  diseased  condition  of  the  brood  called  by  bee  keepers 
"pickle  brood,"  but  practically  nothing  is  known  of  its  cause.  It  is 
characterized  by  a  swollen  watery  appearance  of  the  larva,  usually 
accompanied  by  black  color  of  the  head.     The  larva?  usually  lie  on  their 


backs  in  the  cell,  and  the  head  points  upward.  Tin;  color  j^radually 
changes  from  light  yellow  to  brown  after  the  larva  di(;H.  There  is  no 
ropiness,  and  the  only  odor  is  that  of  sour  decaying  matter,  not  at  all 
like  that  of  American  foul  brood.  In  case  the  larva'  are  capped  over, 
the  cappings  do  not  become  dark,  as  in  the  case  of  the  contagious 
diseases,  but  they  may  be  punctured.  So  far  no  cause  can  be  given 
for  this  disease,  and  whether  or  not  it  is  contagious  is  a  disputed  point. 
Usually  no  treatment  is  necessary  beyond  feeding  during  a  dearth  of 
honey,  but  in  very  rare  cases  when  the  majority  of  larva3  in  a  comb  are 
dead  from  this  cause  the  frame  should  be  removed  and  a  clean  comb 
put  in  its  place  to  make  it  unnecessary  for  the  bees  to  clean  out  so 
much  dead  brood. 

CHILLED,  OVERHEATED,  AND   STARVED    BROOD. 

Many  different  external  factors  may  cause  brood  to  die.  Such  dead 
brood  is  frequently  mistaken,  by  persons  unfamiliar  with  the  brood  dis- 
eases, for  one  or  the  other  of  them.  Careful  examination  will  soon 
determine  whether  dead  brood  is  the  result  of  disease  or  merely  some 
outside  change.  If  brood  dies  from  chilling  or  some  other  such  cause, 
it  is  usually  soon  carried  out  by  the  workers,  and  the  trouble  disappears. 
No  treatment  is  necessary.  Brood  which  dies  from  external  causes 
often  produces  a  strong  odor  in  the  colony,  but  w^holly  unlike  that  of 
American  foul  brood,  merely  that  of  decaying  matter.  The  color  of 
such  brood  varies,  but  the  characteristic  colors  of  the  infectious  diseases 
are  usually  absent,  the  ordinary  color  of  dead  brood  being  more  nearly 
gray. 

Approved : 

James  Wilson, 

Secretary  of  Agriculture. 

Washington,  D.  C,  October  3,  1906. 

O 


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